Some electronic timepieces generally employ as a power source a miniature battery such as a silver oxide cell. As these batteries have a lifetime of one or two years it has been necessary to periodically replace them. In order to preclude this troublesome replacement of batteries, timepieces utilizing solar batteries have been developed and put into practical use. These solar batteries which are semi-permanent in nature convert light energy into electrical energy and are used to charge the power source battery so that it need not be replaced. However, recent years have seen the development and partial marketing of timepieces with circuitry designed to reduce greatly the power consumption. This has made it possible to attain a battery lifetime of as much as 5 years although placing something of a restriction on the timepiece mechanism and battery configuration. A timepiece in which a battery has a 5-year lifetime can therefore be utilized for 10 years by exchanging the battery only once. The end of this 10-year period is considered to represent the end to the lifetime of the timepiece since a timepiece is usually lost or damaged during this interval. In view of this fact, equipping a timepiece with a solar battery complicates the circuitry and construction and hence raises the cost without providing any particularly outstanding advantage. Nevertheless, a solar battery is essential for multi-function digital timepieces and can be effectively used in the future. Specifically, since the illumination lamp and such additional functions as an alarm function in multi-function digital watches consume a considerable amount of power, there is still a requirement for solar batteries in order to ensure extended power source lifetime.
It has heretofore been common practice to solder a plurality of silicon solar batteries in series onto the electrode pattern of a flexible polymide sheet provided with printed wiring and to paste the flexible sheet onto a metal base plate. In order to secure the conventional solar battery base plate it was also ordinary practice to braze legs to the bottom surface of the metal base plate and insert the legs into a module and then secure them with screws. However, in order to reinforce the flexible sheet and straighten its curvature it was necessary to paste the sheet onto a plate such as the metal plate. Accordingly, there was an increase in the number of component parts and in the number of bonding steps.
Attempts have recently been made to reduce the cost of manufacturing these solar battery base plates by forming the printed wiring directly on a glass epoxy resin and then soldering the solar batteries onto the printed wiring. The glass epoxy resin therefore serves as the base plate. However, since legs cannot be brazed onto a glass epoxy resin base plate as they can in the case of the metal base plate, another method of fixing the base plate is required.
It is therefore an object of the present invention to provide a structure for securing a solar battery base plate made of a material such as glass epoxy resin to which legs cannot be attached.